KOFOID AND RIGDEN I SCHIZOGONY IN GONYAULAX. 



343 



known species of the genus. It is evidently closely related to G. 

 triacantha. Further material is necessary to determine the character 

 of this region in the form we have found. 



The accompanying figures, A and B, give the arrangement of plates 

 and structure of the ventral area in G. triacantha. They will make 

 clear the affinities of the organism here described to Gonyaulax and 

 also the general resemblance between G. triacantha and G. catenata, 

 in form, plates, and antapical spines. Our analysis of G. triacantha 

 is based upon actual separation of the elements along the suture 



i/.a. 



Fig. A. Gonyaulax triacantha showing arrangement of plates. 

 Fig B. Ventral view of the same. X 467. 



lines as drawn. The analysis of the theca here given is a correction 

 of the analysis previously given by the senoir author (see Kofoid, 

 1906) in that two anterior intercalaries are added and the inter- 

 pretation of the apical region is modified, one small postcingular 

 1'" is added and the "accessory plate" is here called the posterior 

 intercalary. 



It is not possible to determine from Levander's (1894) or Vanhoffen's 

 (1897) figures of G. catenata or from Levander's discussion whether 

 the skeleton undergoes fission or not, that is whether the chain forma- 

 tion is of the same type as in Ceratium or similar to that described 

 here for G. scries. The fact that the schizonts are of uniform size and 



